PTL1 discloses a three-dimensional measurement device that acquires three-dimensional data (three-dimensional point group data) on multiple points on a measurement target object. The three-dimensional measurement device described in PTL1 irradiates a measurement target object with a pulse laser beam, which is the distance measurement light, and receives reflected light of each pulse laser beam reflected on the measurement target object to measure the distance to the measurement target object. The three-dimensional measurement device further detects a light emitting direction (horizontal and vertical angles) of the distance measurement light to acquire three-dimensional data on the measurement target object. Three-dimensional laser scanners have been generally known as three-dimensional measurement devices disclosed in PTL1.
When the measurement target object is relatively highly reflective, an excessively large amount of reflected light might be reflected from a predetermined portion of the measurement target object, or reflected light with excessively high intensity might be reflected. For example, the three-dimensional measurement device may acquire three-dimensional data on a pipe with a curved surface in a factory. In such a case, the intensity of the reflected light, reflected from the surface of the pipe, might largely vary among portions of the pipe. For another example, the three-dimensional measurement device may acquire three-dimensional data on an area including a road sign having a surface including a reflective material or the like. In such a case, the intensity of the reflected light, reflected from the surface of the sign, might be excessively higher than the intensity of reflected light reflected from a portion other than the surface of the sign. These cases might result in the intensity of the reflected light overwhelming the maximum value of a dynamic range. When this happens, normal scanning by the three-dimensional measurement device might fail to acquire the three-dimensional data on some parts of the measurement target object.
When there is a portion of the measurement target object where the three-dimensional data has failed to be acquired, a measurer might perform the measurement again with a different measurement mode for example. However, this results in longer scanning time of the three-dimensional measurement device. Thus, expansion of the dynamic range and shortening of the scanning time of the three-dimensional measurement device have been called for.
Patent Document 1: Japanese Patent No. 2016-211873